1. Field of the Invention:
The present invention relates to a crushing machine which is used as a principal section of an apparatus for demolishing structures (buildings and the like) made as reinforced concrete, and which is capable of efficiently crushing concrete structural members such as reinforced concrete walls, floors, ceilings, and pillars.
2. Description of the Related Art:
In recent years, there are various types of crushing machines for crushing concrete structural members such as walls and pillars of structures (buildings and the like) made of such as reinforced concrete. Many of these crushing machines are arranged such that a fixed jaw and a movable jaw are provided in such a manner as to be freely opened or closed by a hydraulic cylinder mechanism or the like, and the concrete structural members are crushed by crushing blades which are respectively provided on the fixed jaw and the movable jaw.
Crushing blades formed substantially in the shape of a half-split bead of a soroban, or an abacus, i.e., crushing blade having a semicircular profile, are used widely, as disclosed in Japanese Patent Application Publication No. 43513/1985. The mechanism of this a semicircular crushing blade operates such that, during the crushing of a concrete structural member, the crushing blade first bites into the concrete structural member, which is clamped by the fixed jaw and the movable jaw, in the manner of a wedge, the concrete structural member then becomes cracked as the depth of the bite becomes deeper, and the concrete structural member is crushed as the cracks become wider.
In particular, among semicircular crushing blades formed substantially in the shape of a half-split bead of a soroban, there is a type in which the side elevational shape is not completely semicircular but trapezoidal, and the front edge side is substantially right-angled, while the rear edge side is formed in the shape of a circular arc. This type of movable-side crushing blade is provided such that an arcuate blade portion on the rear edge side thereof opposes the fixed jaw located therebelow.
With such a movable-side crushing blade, the movable-side crushing blade formed bites into and cracks the concrete structural member as described above, thereby making it possible to crush the concrete structural member such as a wall, a pillar, and the like. In particular, as shown in FIG. 17, where the side elevational shape of the crushing blade is trapezoidal with its front edge side formed in a substantially right-angled shape and with its overall rear edge side formed substantially in the shape of a circular arc, when the movable jaw is closed to clamp the concrete structural member in cooperation with the fixed jaw, the rear edge side of the crushing blade is first brought into contact with the concrete structural member to crush the concrete structural member.
Then, the arcuate blade portion pierces the surface of the concrete structural member over a relatively large range, and makes it possible to crush the concrete structural member while cracking that portion of the concrete structural member almost instantly. The crushing blade of this type is very effective in a case where the internal structure of the concrete structural member itself has become relatively fragile.
However, among the concrete structural members, particularly in the case of a concrete structural member in which the density of a concrete component is high, the concrete structural member is very hard, and resistance during crushing may be very large. When such a particularly hard concrete structural member is crushed, in the case of the crushing blade with its overall rear edge side formed in the shape of a circular arc, a portion of contact of the movable-side crushing blade with respect to the concrete structural member during an initial period of crushing extends over a long range, and assumes a state of line contact.
Hence, the force for crushing is dispersed at the contact surface which is in the state of line contact, and the crushing force becomes relatively small per unit area, thereby making it very difficult to effect crushing. Further, with the conventional types of crushing machines, slippage can occur between the crushing blades and the concrete structural member when the concrete structural member is crushed, so that the concrete structural member is frequently dislocated from the fixed jaw and the movable jaw, resulting in a decline in the efficiency of the crushing operation.
Particularly in the case of a large pillar-shaped member whose cross section is substantially square or rectangular, the pillar-shaped member must be crushed at its right-angled corner portions, which means that portions of two wall surfaces which join at right angles are crushed by the two crushing blades. In this case, the two wall surfaces which join at right angles constitute relatively sharply inclined surfaces with respect to the two crushing blades that are provided on the fixed jaw and the movable jaw. Accordingly, when an attempt is made to effect a crushing operation at the two wall surfaces which join at right angles by means of the two crushing blades, the crushing blades tend to slip on the wall surfaces before they bite into the wall surfaces.
Thus, the crushing operation at a right-angled corner portion of such a rectangular pillar-shaped member has been very difficult.